The present invention generally relates to a disk apparatus for compressing, in terms of time, the data of the respective channels of signals having a plurality of channels of image signals, by voice signals and so on, and separating, recording each of them on a disk recording medium.
In recent years, the chances of editing images or sounds are considerably increased in number because of developments in information communication fields. Especially demands for editing has increased in broadcasting stations. Operationality is considered to be important in the editing operation. Especially the contraction of the editing operating time is most important. In the editing operation, a series of operations such as a plurality of file retrieval operations, reproducing operations, optional processing operations, recording operations on information recording media again are effected. There are magnetic tape, magnetic disks, optical disks and so on as information recording media to be used in the editing operation.
A plurality of tracks can be recorded, and reproduced at the same time in the recording, and reproducing apparatus using magnetic tape, because a plurality of parallel tracks can be provided on the magnetic tape. But the file retrieving operation has a defect in that the retrieving speed is slow, because only the retrieving operation in a primary direction such as fast forward or playback can be effected with respect to the tape. The magnetic tape or the magnetic head wears out due to friction, because the magnetic tape is in direct contact against the magnetic head which is adapted to record, and reproduce the information on it.
As the pick up operation for reading out the information can be freely moved on the recording face in the magnetic disk or the optical disk, the file retrieving operation can be effected at higher speeds in a secondary dimension.
Although a magnetic disk or an optical disk is capable of being used in a high speed retrieving operation, it is basically impossible to handle a plurality of tracks, or to record or reproduce many channels at the case of same time as in the magnetic tape, because the magnetic disk and the optical disk basically have only one pick up. The information recording operation of a plurality of channels can be effected if the information is compressed in terms of time and the information of each channel is recorded by time division. It is actually effected on a CD or the like.
It is difficult to extract with high speed the information of a specific channel only, because the information recorded in this manner is minutely arranged in a primary dimension with the respective channels being provided by time division. It is difficult to record the other channel at the same time, while reproducing a specific channel using an apparatus capable of recording, and reproducing operations when the information of the respective channels are minutely arranged in the primary dimension. This is because stricter accuracy is required to distinguish among the recording regions of the respective channels, and the laser power has to be often switched often with the recording operation and the reproducing operation, and so on.